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[texts]String Theory - J. L. F. Barbon
This is a rendering of a review talk on the state of String Theory, given at the EPS-2003 Conference, intended for a wide audience of experimental and theoretical physicists. It emphasizes general ideas rather than technical aspects.
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[texts]Causal set as a discretized phase spacetime - Roman Sverdlov
The first goal of this paper is to show that discreteness, locality, and relativistic covariance can peacefully coexist if the ordinary spacetime (OST) is replaced with phase spacetime (PST) as a geometric background of a Poisson process, where PST is a spacetime generalization of a notion of phase space (this is a 7-dimensional version of the 8-dimensional structure proposed by Caianiello). Furthermore, Caianiello's idea of finite acceleration is implemented...
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[texts]Chronon corrections to the Dirac equation - Andrei A. Galiautdinov
The Dirac equation is not semisimple. We therefore regard it as a contraction of a simpler decontracted theory. The decontracted theory is necessarily purely algebraic and non-local. In one simple model the algebra is a Clifford algebra with 6N generators. The quantum imaginary $\hbar i$ is the contraction of a dynamical variable whose back-reaction provides the Dirac mass. The simplified Dirac equation is exactly Lorentz invariant but its symmetry group is SO(3,3), a decontraction of the Poinca...
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[texts]Microwave-induced flow of vortices in long Josephson junctions - F. L. Barkov
We report experimental and numerical study of microwave-induced flow of vortices in long Josephson junctions at zero dc magnetic field. Our intriguing observation is that applying an ac-bias of a small frequency $f \ll f_p $ and sufficiently large amplitude changes the current-voltage characteristics ($I$-$V$ curve) of the junction in a way similar to the effect of dc magnetic field, well known as the flux-flow behavior...
Downloads: 2
[texts]Non-Critical Pure Spinor Superstrings - Ido Adam
We construct non-critical pure spinor superstrings in two, four and six dimensions. We find explicitly the map between the RNS variables and the pure spinor ones in the linear dilaton background. The RNS variables map onto a patch of the pure spinor space and the holomorphic top form on the pure spinor space is an essential ingredient of the mapping. A basic feature of the map is the requirement of doubling the superspace, which we analyze in detail...
[texts]Dissipation and Vortex Creation in Bose-Einstein Condensed Gases - B. Jackson
We solve the Gross-Pitaevskii equation to study energy transfer from an oscillating `object' to a trapped Bose-Einstein condensate. Two regimes are found: for object velocities below a critical value, energy is transferred by excitation of phonons at the motion extrema; while above the critical velocity, energy transfer is via vortex formation. The second regime corresponds to significantly enhanced heating, in agreement with a recent experiment.
[texts]HST Proper Motion confirms the optical identification of the nearby pulsar PSR 1929+10 - Roberto P. Mignani
We report on the proper motion measurement of the proposed optical counterpart of the X-ray/radio pulsar PSR 1929+10. Using images obtained with the HST/STIS (average epoch 2001.73) we computed a yearly displacement of +97 +/- 1 mas yr^{-1} in RA and +46 +/- 1 mas yr^{-1} in Dec since the epoch (1994.52) of the original HST/FOC detection. Both the magnitude and direction of the optical proper motion components are found to be fully consistent with the most recent VLBA radio measurements...
[texts]Differences Between Hole and Electron Doping of a Two-Leg CuO Ladder - S. Nishimoto
Here we report results of a density-matrix-renormalization-group (DMRG) calculation of the charge, spin, and pairing properties of a two-leg CuO Hubbard ladder. The outer oxygen atoms as well as the rung and leg oxygen atoms are included along with near-neighbor and oxygen-hopping matrix elements. This system allows us to study the effects of hole and electron doping on a system which is a charge transfer insulator at a filling of one hole per Cu and exhibits power law, d-wave-like pairing corre...
[texts]The incomplete beta function law for parallel tempering sampling of classical canonical systems - Cristian Predescu
We show that the acceptance probability for swaps in the parallel tempering Monte Carlo method for classical canonical systems is given by a universal function that depends on the average statistical fluctuations of the potential and on the ratio of the temperatures. The law, called the incomplete beta function law, is valid in the limit that the two temperatures involved in swaps are close to one another...
Downloads: 1
[texts]Fermi-edge problem in the presence of AC electric field - Yi Zhou
We study in this paper a non-equilibrium Fermi-edge problem where the system under investigation is a single electron reservoir putting under an AC electric field. We show that the electron Green's function and other correlation functions in the problem can be solved and expressed exactly in terms of a well-defined integral. The qualitative behaviors of the solution is studied and compared with the situation where the impurity is coupled to more than one reservoirs at different chemical potentia...
Downloads: 3
[texts]Supernova neutrinos in the light of FCNC - S. W. Mansour
We study the effect of including flavor changing neutral currents (FCNC) in the analysis of the neutrino signal of a supernova burst. When we include the effect of the FCNC which are beyond the standard model (SM) in the study of the MSW resonant conversion, we obtain dramatic changes in the \Delta m^2-sin^2(2\theta) probability contours for neutrino detection.
Downloads: 1
[texts]Scaling laws for Shor's algorithm with a banded quantum Fourier transform - Y. S. Nam
We investigate the performance of a streamlined version of Shor's algorithm in which the quantum Fourier transform is replaced by a banded version that for each qubit retains only coupling to its $b$ nearest neighbors. Defining the performance $P(n,b)$ of the $n$-qubit algorithm for bandwidth $b$ as the ratio of the success rates of Shor's algorithm equipped with the banded and the full bandwidth ($b=n-1$) versions of the quantum Fourier transform, our numerical simulations show that $P(n,b) \ap...
Downloads: 1
[texts]Dimensional regularization of the gravitational interaction of point masses - Thibault Damour
We show how to use dimensional regularization to determine, within the Arnowitt-Deser-Misner canonical formalism, the reduced Hamiltonian describing the dynamics of two gravitationally interacting point masses. Implementing, at the third post-Newtonian (3PN) accuracy, our procedure we find that dimensional continuation yields a finite, unambiguous (no pole part) 3PN Hamiltonian which uniquely determines the heretofore ambiguous ``static'' parameter: namely, $\omega_s=0$...
Downloads: 1
[texts]Equivalence-Checking on Infinite-State Systems: Techniques and Results - Antonin Kucera
The paper presents a selection of recently developed and/or used techniques for equivalence-checking on infinite-state systems, and an up-to-date overview of existing results (as of September 2004).
[texts]The microscopic meaning of grand potential: cluster properties of the one-dimensional lattice gas - Agata Fronczak
We demonstrate, with a concrete example, how the combinatorial approach to a general system of particles, which was introduced in detail in the earlier paper arXiv:1205.4986, works and where it enters to provide a genuine extension of results obtainable by more traditional methods of statistical mechanics. To this end, an effort is made to study cluster properties of the one-dimensional lattice gas with nearest neighbor interactions...
[texts]On excess filtration on the Steenrod algebra - Atsushi Yamaguchi
In this note, we study some properties of the filtration of the Steenrod algebra defined from the excess of admissible monomials. We give several conditions on a cocommutative graded Hopf algebra A^* which enable us to develop the theory of unstable A^*-modules.
Downloads: 2
[texts]Fibonacci-Hubbard Chain at Zero and Finite Temperatures - Sanjay Gupta
We have studied finite-sized single band Hubbard chains with Fibonacci modulation for half filling within a mean field approximation. The ground state properties, together with the dc conductivity both at zero and non-zero temperatures, are calculated for such quasi-periodic Hubbard chains. While a reduction in the conductivity is found for strong electronic interaction or strong Fibonacci modulation, a competition between these two is observed to enhance the conductivity...
Downloads: 1
[texts]Classical and quantum spinor cosmology with signature change - B. Vakili
We study the classical and quantum cosmology of a universe in which the matter source is a massive Dirac spinor field and consider cases where such fields are either free or self-interacting. We focus attention on the spatially flat Robertson-Walker cosmology and classify the solutions of the Einstein-Dirac system in the case of zero, negative and positive cosmological constant $\Lambda$. For $\Lambda
[texts]On Measuring Chemical Abundances in Distant Galaxies Using Global Emission Line Spectra - Henry A. Kobulnicky
The advent of 8--10 meter class telescopes enables direct measurement of the chemical properties in the ionized gas of cosmologically--distant galaxies with the same nebular analysis techniques used in local H II regions. We show that spatially unresolved (i.e., global) emission line spectra can reliably indicate the chemical properties of distant star-forming galaxies. However, standard nebular chemical abundance measurement methods (those with a measured electron temperature from [O III] lambd...
[texts]Search for new particles decaying into dijets in proton-antiproton collisions at sqrt(s) = 1.96 TeV - The CDF Collaboration
We present a search for new particles whose decays produce two jets (dijets) using proton-antiproton collision data corresponding to an integrated luminosity of 1.13 fb-1 collected with the CDF II detector. The measured dijet mass spectrum is found to be consistent with next-to-leading-order perturbative QCD predictions, and no significant evidence of new particles is found. We set upper limits at the 95% confidence level on cross sections times the branching fraction for the production of new p...
Downloads: 2
[texts]On the Completeness of the Black Hole Singularity in 2d Dilaton Theories - M. O. Katanaev
The black hole of the widely used ordinary 2d--dilaton model (DBH) deviates from the Schwarzschild black hole (SBH) of General Relativity in one important feature: Whereas non-null extremals or geodesics show the expected incompleteness this turns out {\it not to be the case for the null extremals}. After a simple analysis in Kruskal coordinates for singularities with power behavior of this -- apparently till now overlooked -- property we discuss the global structure of a large family of general...
Downloads: 2
[texts]Complexity of super-coherence problems in ASP - Mario Alviano
Adapting techniques from database theory in order to optimize Answer Set Programming (ASP) systems, and in particular the grounding components of ASP systems, is an important topic in ASP. In recent years, the Magic Set method has received some interest in this setting, and a variant of it, called DMS, has been proposed for ASP. However, this technique has a caveat, because it is not correct (in the sense of being query-equivalent) for all ASP programs...
Downloads: 2
[texts]Dependence of the evolution of the cavity radiation of a coherently pumped correlated emission laser on dephasing and phase fluctuation - Sintayehu Tesfa
Analysis of the dynamics of the cavity radiation of a coherently pumped correlated emission laser is presented. The phase fluctuation and dephasing are found to affect the time evolution of the two-mode squeezing and intensity of the cavity radiation significantly. The intensity and degree of the two-mode squeezing increase at early stages of the process with time, but this trend changes rapidly afterwards...
Downloads: 1
[texts]arxiv-1206.1766
[texts]Estimates for parameters and characteristics of the confining SU(3)-gluonic field in π^0-meson from one- and two-photon decays - Yu. P. Goncharov
On the basis of the confinement mechanism earlier proposed by author the electric formfactor of $\pi^0$-meson is nonperturbatively calculated. The latter is then applied to describing electromagnetic decays $\pi^0\to2\gamma$ and $\pi^0\to e^+e^-\gamma$ which entails estimates for parameters of the confining SU(3)-gluonic field in $\pi^0$-meson. The corresponding estimates of the gluon concentrations, electric and magnetic colour field strengths are also adduced for the mentioned field.
[texts]The Sixth-Moment Sum Rule For the Pair Correlations of the Two-Dimensional One-Component Plasma: Exact Result - P. Kalinay
The system under consideration is a two-dimensional one-component plasma in fluid regime, at density n and at arbitrary coupling Gamma=beta e^2 (e=unit charge, beta = inverse temperature). The Helmholtz free energy of the model, as the generating functional for the direct pair correlation c, is treated in terms of a convergent renormalized Mayer diagrammatic expansion in density. Using specific topological transformations within the bond-renormalized Mayer expansion we prove that the nonzero con...
Downloads: 1
[texts]Excited Baryons in Large Nc QCD: Matching the 1/Nc expansion to quark models using the permutation group S_N - Dan Pirjol
We show how to match quark models to the 1/Nc expansion of QCD. As an example we discuss in detail the mass operator of orbitally excited baryons and match it to the one-gluon exchange and the one-boson exchange variants of the quark model. The matching procedure is very general and makes use of the transformation properties of states and operators under S_N^{orb} \times S_N^{sp-fl}, the permutation group acting on the orbital and spin-flavor degrees of freedom of N quarks.
Downloads: 2
[texts]On Communication Protocols that Compute Almost Privately - Marco Comi
A traditionally desired goal when designing auction mechanisms is incentive compatibility, i.e., ensuring that bidders fare best by truthfully reporting their preferences. A complementary goal, which has, thus far, received significantly less attention, is to preserve privacy, i.e., to ensure that bidders reveal no more information than necessary. We further investigate and generalize the approximate privacy model for two-party communication recently introduced by Feigenbaum et al.[8]...
Downloads: 2
[texts]On the properties of the exchange graph of a cluster algebra - Michael Gekhtman
We prove a conjecture about the vertices and edges of the exchange graph of a cluster algebra $\A$ in two cases: when $\A$ is of geometric type and when $\A$ is arbitrary and its exchange matrix is nondegenerate. In the second case we also prove that the exchange graph does not depend on the coefficients of $\A$. Both conjectures were formulated recently by Fomin and Zelevinsky.
[texts]Minimal triangulations of sphere bundles over the circle - Bhaskar Bagchi
For integers $d \geq 2$ and $\epsilon = 0$ or 1, let $S^{1, d - 1}(\epsilon)$ denote the sphere product $S^{1} \times S^{d - 1}$ if $\epsilon = 0$ and the twisted $S^{d - 1}$ bundle over $S^{1}$ if $\epsilon = 1$. The main results of this paper are: (a) if $d \equiv \epsilon$ (mod 2) then $S^{1, d - 1}(\epsilon)$ has a unique minimal triangulation using $2d + 3$ vertices, and (b) if $d \equiv 1 - \epsilon$ (mod 2) then $S^{1, d - 1}(\epsilon)$ has minimal triangulations (not unique) using $2d + ...
[texts]The Geometry of the Elongated Phase in 4-D Simplicial Quantum Gravity - Gabriele Gionti
We discuss the elongated phase of 4D simplicial quantum gravity by exploiting recent analytical results. In particular using Walkup's theorem we prove that the dominating configurations in the elongated phase are tree-like structures called "stacked spheres". Such configurations can be mapped into branched polymers and baby universes arguments are used in order to analyse the critical behaviour of theory in the weak coupling regime.
Downloads: 1
[texts]On electronic shells surrounding charged insulated metallic clusters - K. Dietrich
We determine the wavefunctions of electrons bound to a positively charged mesoscopic metallic cluster covered by an insulating surface layer. The radius of the metal core and the thickness of the insulating surface layer are of the order of a couple of angstroems. We study in particular the electromagnetic decay of externally located electrons into unoccupied internally located states which exhibits a resonance behaviour...
Downloads: 2
[texts]Comment: Struggles with Survey Weighting and Regression Modeling - Danny Pfeffermann
Comment: Struggles with Survey Weighting and Regression Modeling [arXiv:0710.5005]
Downloads: 1
[texts]SiFTO: An Empirical Method for Fitting SNe Ia Light Curves - A. Conley
We present SiFTO, a new empirical method for modeling type Ia supernovae (SNe Ia) light curves by manipulating a spectral template. We make use of high-redshift SN observations when training the model, allowing us to extend it bluer than rest frame U. This increases the utility of our high-redshift SN observations by allowing us to use more of the available data. We find that when the shape of the light curve is described using a stretch prescription, applying the same stretch at all wavelengths...
[texts]Time evolution of decay of two identical quantum particles - Gastón García-Calderón
An analytical solution for the time evolution of decay of two identical non interacting quantum particles seated initially within a potential of finite range is derived using the formalism of resonant states. It is shown that the wave function, and hence also the survival and nonescape probabilities, for factorized symmetric and entangled symmetric/antisymmetric initial states evolve in a distinctive form along the exponentially decaying and nonexponential regimes...
Downloads: 2
[texts]Cylindrical surface plasmon mode coupling as a three-dimensional Kaluza- Klein theory - Igor I. Smolyaninov
Cylindrical surface plasmon (CSP) mode coupling in a nanowire or a nanochannel is described in terms of three-dimensional Kaluza-Klein theory in which the compactified third dimension is considered to be the angular coordinate of the metal cylinder. Higher (n>0) CSP modes are shown to posses a quantized effective charge proportional to their angular momentum n. In a nanowire these slow moving charges exhibit strong long-range interaction via fast massless CSPs with zero angular momentum (n=0)...
Downloads: 2
[texts]Witten-Nester Energy in Topologically Massive Gravity - Ergin Sezgin
We formulate topologically massive supergravity with cosmological constant in the first order formalism, and construct the Noether supercurrent and superpotential associated with its local supersymmetry. Using these results, we construct in ordinary topologically massive gravity the Witten-Nester integral for conserved charges containing spinors which satisfy a generalized version of Witten equation on the initial value surface...
Downloads: 2
[texts]The absorption spectrum of V838 Mon in 2002 February - March. I. Atmospheric parameters and iron abundance - B. M. Kaminsky
We present a determination of the effective temperatures, iron abundances, and microturbulent velocities for the pseudophotosphere of V838 Mon on 2002 February 25, and March 2 and 26. Physical parameters of the line forming region were obtained in the framework of a self-consistent approach, using fits of synthetic spectra to observed spectra in the wavelength range 5500-6700A. We obtained Tef = 5330, 5540 and 4960 K, for February 25, March 2, and March 26, respectively...
Downloads: 2
[texts]MSW effect with flavor changing interactions and the atmospheric neutrino problem - J. C. Montero
We consider flavor changing effective neutrino interactions in the context of massive neutrinos in the issue of atmospheric neutrinos. Assuming as usual that this is an indication of the oscillation of muon neutrinos into tau neutrinos we show that there is a set of parameters which is consistent with the MSW resonance condition for the typical Earth density and atmospheric neutrino energies. In particular we show that even if the vacuum mixing angle vanishes it is still possible to have a reson...
[texts]Precise Measurement of Gravity Variations During a Total Solar Eclipse - Qian-shen Wang
The variations of gravity were measured with a high precision LaCoste-Romberg D gravimeter during a total solar eclipse to investigate the effect of solar eclipse on the gravitational field. The observed anomaly $(7.0 \pm 2.7) \times 10^{-8}$ m/s$^2$ during the eclipse implies that there may be a shielding property of gravitation.
Downloads: 2
[texts]Hyperon-nucleon force from lattice QCD - H. Nemura
We calculate potentials between a proton and a $\Xi^0$ (hyperon with strangeness -2) through the equal-time Bethe-Salpeter wave function, employing quenched lattice QCD simulations with the plaquette gauge action and the Wilson quark action on (4.5 fm)^4 lattice at the lattice spacing $a \simeq 0.14$ fm. The ud quark mass in our study corresponds to $m_{\pi}\simeq 0.37$ and 0.51 GeV, while the s quark mass corresponds to the physical value of $m_K$...
[texts]arxiv-1206.4117
[texts]Lensless ghost imaging with true thermal light - Xi-Hao Chen
We report the first (to our knowledge) experimental demonstration of lensless ghost imaging with true thermal light. Although there is no magnification, the method is suitable for all wavelengths and so may find special applications in cases where it is not possible to use lenses, such as with x-rays or gamma-rays. We also show numerically that some magnification may be realized away from the focal plane, but the image will always be somewhat blurred.
Downloads: 3
[texts]A change of variable formula with Itô correction term - Krzysztof Burdzy
We consider the solution $u(x,t)$ to a stochastic heat equation. For fixed $x$, the process $F(t)=u(x,t)$ has a nontrivial quartic variation. It follows that $F$ is not a semimartingale, so a stochastic integral with respect to $F$ cannot be defined in the classical It\^{o} sense. We show that for sufficiently differentiable functions $g(x,t)$, a stochastic integral $\int g(F(t),t)\,dF(t)$ exists as a limit of discrete, midpoint-style Riemann sums, where the limit is taken in distribution in the...
Downloads: 1
[texts]Sky Subtraction with Fiber-Spectrographs - C. Lissandrini
The sky subtraction performances of multi-fiber spectrographs are discussed, analysing in detail the case of the OPTOPUS system at the 3.6 meter ESO telescope at La Silla. A standard technique, based on flat-fields obtained with a uniformly illuminated screen on the dome, provides poor results. A new method has been developed, using the [OI] emission line at 5577 \AA\ as a calibrator of the fiber transmittance, taking into account the diffuse light and the influence of each fiber on the adjacent...
Downloads: 4
[texts]Macroscopic two-state systems in trapped atomic condensates - Dmitry Solenov
We consider a macroscopic two-sate system based on persistent current states of a Bose-Einstein condensate (BEC) of interacting neutral atoms confined in a ring with a weak Josephson link. We demonstrate that macroscopic superpositions of different BEC flows are energetically favorable in this system. Moreover, a macroscopic two-state dynamics emerges in the low energy limit. We also investigate fundamental limitations due to the noise inherent to the interacting BEC of Josephson-ring geometry...
[texts]Two-pion exchange potential and the $πN$ amplitude - M. T. Peña
We discuss the two-pion exchange potential which emerges from a box diagram with one nucleon (the spectator) restricted to its mass shell, and the other nucleon line replaced by a subtracted, covariant $\pi N$ scattering amplitude which includes $\Delta$, Roper, and $D_{13}$ isobars, as well as contact terms and off-shell (non-pole) dressed nucleon terms. The $\pi N$ amplitude satisfies chiral symmetry constraints and fits $\pi N$ data below $\sim$ 700 MeV pion energy...
Downloads: 1
[texts]WASP-54b, WASP-56b and WASP-57b: Three new sub-Jupiter mass planets from SuperWASP - F. Faedi
We present three newly discovered sub-Jupiter mass planets from the SuperWASP survey: WASP-54b is a heavily bloated planet of mass 0.636$^{+0.025}_{-0.024}$ \mj and radius 1.653$^{+0.090}_{-0.083}$ \rj. It orbits a F9 star, evolving off the main sequence, every 3.69 days. Our MCMC fit of the system yields a slightly eccentric orbit ($e=0.067^{+0.033}_{-0.025}$) for WASP-54b. We investigated further the veracity of our detection of the eccentric orbit for WASP-54b, and we find that it could be re...
Downloads: 3
[texts]Chemical Evolution models of Local Group galaxies - M. Tosi
Status quo and perspectives of standard chemical evolution models of Local Group galaxies are summarized, discussing what we have learnt from them, what we know we have not learnt yet, and what I think we will learn in the near future. It is described how Galactic chemical evolution models have helped showing that: i) stringent constraints on primordial nucleosynthesis can be derived from the observed Galactic abundances of the light elements, ii) the Milky Way has been accreting external gas fr...
Downloads: 2
[texts]arxiv-1208.1374
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